Evanescent field-based sensors are fast becoming a technology of choice for accurate label-free detection of biological reactions. In recent years, the biological, pharmaceutical, and other research communities have begun to recognize that evanescent field-based sensors can be useful, high-throughput research tools to measure a variety of biological or biochemical functions. This technology typically involves the use of an optical evanescent field to sense changes in the local environment (refractive index) where a biological or chemical reaction takes place. A grating or prism can be used to couple light in and out of an optical mode, thereby probing the effective index of the mode, which changes together with the surface index. Changes in the angle or wavelength of the probe light, for example, indicate changes of the waveguide effective index that result from activity at the sensor surface. Evanescent field sensors have demonstrated high sensitivity, and an ability to detect binding reactions of as little as about 250 Da molecular weight (e.g., biotin binding to streptavidin). Typical spore-based pathogens (e.g., anthrax) are fairly massive (≧20-50 kDa) entities compared to tiny pharmaceutical drug candidates that are the more traditional target of evanescent technology. As a result, such sensors and instruments should be sufficiently sensitive for airborne pathogen detection. Furthermore, because of their responsiveness to index of refraction, these kinds of sensors also respond to chemicals, and can therefore likewise detect chemical toxins.